carbon dioxide in the atmosphere

Carbon dioxide (CO2) in the Earth's atmosphere goes through a path that is vaguely reminiscent of the water cycle known to everyone since childhood in nature. Its meaning boils down to the fact that CO2 appears in the air due to natural and man-made processes, and then partly removed from the atmosphere, and partly accumulates in its upper layers and affects the climate.

Distribution of CO2 in the Earth's atmosphere

For many centuries, right up to the beginning of the industrial revolution, natural processes served as the main sources of CO2 formation: volcanic eruptions, decomposition of organic matter, forest fires and animal respiration. But from about the middle of the XVIII century. the content of CO2 in the air begins to be significantly affected by human industrial activity, primarily those that are associated with the combustion of fossil fuels (oil, coal, shale, natural gas, etc.) and the production of cement. They account for about 75% of anthropogenic CO2 emissions. Land use is responsible for the remaining 25%, in particular, active deforestation.

The removal of part of CO2 from the air occurs due to its dissolution in the ocean and absorption by plants. However, plants not only absorb carbon dioxide, but also release it: in the process of breathing, they, like people, “inhale” oxygen and “exhale” CO2. So carbon dioxide is always present in the atmosphere, the only question is how much it is.

Behind recent decades CO2 content is rising faster than ever before in the documentary history. In 1750, the concentration of CO2 in the atmosphere was about 270 ppm, and only after more than two hundred years, by 1958, did it "creep" to the mark of 320 ppm. Another fifty years - and a leap of as much as 60 points: in 2005, the CO2 content in the atmosphere was 380 ppm. In 2010 - already 395 ppm. Recently, scientists reported that the content carbon dioxide exceeded 400 ppm and will not return in the foreseeable future. Looks like it's time to rewrite encyclopedias.

By the way, in the history of the Earth there were periods with a much higher content of carbon dioxide. Four billion years ago, our young planet's atmosphere contained as much as 90% CO2. True, life had not yet originated: there was no oxygen at all. 2.5 billion years ago, plants appeared and everything was fine.

I must say that the mark of 400 ppm was overcome before. The content of CO2 in the atmosphere varies throughout the year, reaching a maximum in May. So the spring-summer increase in the concentration of carbon dioxide did not cause concern to scientists. In May 2015, even in Antarctica, CO2 levels reached 400 ppm, which has not happened in 4 million years! But on the other hand, in September, the lowest CO2 content in the atmosphere of the year is traditionally observed. Therefore, the September overcoming of the 400 ppm mark is the clearest evidence of an uncontrolled increase in the amount of carbon dioxide in the air.

carbon dioxide and we

What will happen to us in this “new four-hundred-pipiem world,” as the Western press managed to christen our planet? The answer can be summed up in two words: global warming.

Global warming began a long time ago, and it is directly related to the content of carbon dioxide in the atmosphere. The fact is that CO2 is not just a gas, but a greenhouse gas. CO2 is extremely inert, it is reluctant to react with other chemical elements. Due to this, it accumulates in the Earth's atmosphere, where it retains thermal radiation from its surface and prevents its return to space. This is the greenhouse effect.

The greenhouse effect is so strongly associated in our minds with global warming that it is usually associated with something negative. Meanwhile, it is the greenhouse effect that we owe a comfortable life on Earth. Without greenhouse gases(in addition to CO2, these include water vapor, methane and ozone) the average temperature on the planet would be -15 ° C, and not + 15 ° C, as it is now.

But an uncontrolled increase in the content of greenhouse gases leads to an increase in the greenhouse effect, which, in turn, leads to global warming. Everyone has heard about it and often treats it with irony, and sometimes with suspicion: is this a conspiracy of eco-fuel producers? The thing is that we seem to see no signs of global warming in Everyday life.

Indeed, global warming is a slow process. Greenland will not melt tomorrow, or the day after tomorrow, or even in a hundred years. There will be no giant wave washing away New York like in disaster movies. It will be flooded gradually: the city will have to retreat under the onslaught of the rising ocean. Small Pacific islands will disappear from the face of the Earth (or rather, the sea). Wet regions will become even wetter, and dry regions even drier. In the first, disease-carrying insects will breed, in the second, an acute shortage of food will begin and drinking water. The influx of fresh glacial water into the ocean will change the course of warm and cold currents, which threatens to cool in the Northern Hemisphere and hurricanes around the planet. You can not continue further: even if a small part of these predictions come true, humanity will have a hard time.

In the meantime, the average annual temperature around the world has been breaking records for the third year in a row. 2016 is called the hottest year in the last 150 years. Scientists have found that the Earth's atmosphere has warmed by 1.45°C compared to the pre-industrial period. The figure may seem insignificant, but it is more than enough to melt the ice.

See for yourself:

Ice melting (NASA photos)

Vyacheslav Viktorovich Alekseev, Doctor of Physical and Mathematical Sciences, Head of the Laboratory of Renewable Energy Sources, Faculty of Geography, Lomonosov Moscow State University. Specialist in the field of mathematical and physical modeling of geophysical systems.

Sofya Valentinovna Kiseleva, Candidate of Physical and Mathematical Sciences, senior researcher at the same laboratory. He is engaged in physical modeling of the processes of carbon dioxide transport, the problems of modern climate change.

Nadezhda Ivanovna Chernova, Candidate of Biological Sciences, senior researcher at the same laboratory. Deals with environmental aspects of application solar energy, problems of rational use of natural resources.

In early 1998, the former president of the US National Academy of Sciences F. Seitz submitted a petition to the scientific community for consideration, calling on the governments of the United States and other countries to reject the signing of the agreements reached in Kyoto in December 1997 to limit greenhouse gas emissions. The petition was accompanied by an information brief titled “The Environmental Impact of Rising Carbon Dioxide in the Atmosphere” . It contained a selection of published scientific results designed to prove not only the absence of empirical evidence to support the future warming predicted by many scientists, but also the undoubted benefit to mankind from the growth of greenhouse gases. The following theses were put forward in the review.

The current increase in CO 2 in the atmosphere comes after almost 300 years of warming. Therefore, this growth may not be the result of human activity, but a consequence of a natural process - the intensification of CO 2 release by the ocean with an increase in water temperature. In addition, compared with the annual anthropogenic input of carbon into the atmosphere (5.5 Gt), its content even in the reservoirs of the mobile fund (in the atmosphere - about 750 Gt, in the surface layers of the ocean - 1000 Gt, near-Earth biota, including soils and detritus, - about 2200 Gt) is so large that it is difficult to recognize the anthropogenic growth factor of CO2 in the atmosphere as significant.

Further, the authors of the review present numerous data from satellite measurements of the temperature of the lower troposphere (at an altitude of about 4 km) for the period 1958–1996. and note that since 1979 there has been a weak negative trend in the average global temperature (–0.047°C over 10 years). In the USA, over the past 10 years, the surface air temperature has decreased by 0.08°C.

At the same time, weather station data show positive trends in surface layer temperatures (+0.07°C over 10 years). Discrepancies in results cause modeling of future climate change based on temperature rise data to lead to incorrect predictions. Discussing computer models of the greenhouse effect and climate warming, the authors of the review emphasize that the climate is a complex, non-linear dynamic system. The uncertainties of the influence, for example, of ocean surface currents, heat transfer in the ocean, humidity, cloudiness, etc., according to the authors, are so large in comparison with the influence of CO 2 that the model estimates of the modern temperature course differ significantly from the available empirical data. Numerous feedbacks of the climate system, which are poorly reflected in models, also lead to errors in forecasts and inconsistencies with reality.

Criticizing the quality of data from ground-based air temperature measurements, the authors of the review refer to the thermal impact of urbanized areas, which distorts the real picture of the relationship between the increase in greenhouse gas concentrations and changes in atmospheric temperature. There is nothing unusual about modern climate changes; these are only natural changes caused by both internal earthly variations and external ones - in particular, fluctuations in solar activity. Satellite data obtained, however, for only four years (1993-1997), according to the authors, do not show any changes in ocean level, as predicted by global warming models. The number of severe tropical hurricanes in the Atlantic during the period 1940-1997. and the maximum wind speed in them decreased, which also contradicts both the idea of ​​global warming and the model results.

Here it should be emphasized that the existence of more than a dozen climate-forming factors is generally recognized. The following stand out as the most significant:

In a study by V.V. Klimenko and colleagues, the impact of these factors on the radiation balance was analyzed within a decade and the last century. When considering the secular climate variability, it turned out that it was the accumulation of greenhouse gases in the atmosphere that determined the increase in the average global temperature by 0.5°C. However, the authors emphasize that the explanation of current and future climate changes only by the anthropogenic factor rests on a very shaky foundation, although its role is certainly increasing with time.

Of particular interest is the recent work of S. Korti with colleagues, in which the observed warming in the Northern Hemisphere is also associated mainly with natural changes in the atmospheric circulation regimes. True, its authors emphasize that this fact cannot serve as proof of the absence of anthropogenic impact on the climate. A detailed model analysis of the role of the same climatic factors in the increase in the average surface air temperature was recently carried out by British scientists. Their results show that the warming of the atmosphere in the first half of the 20th century. (between 1910 and 1940) was mainly due to fluctuations in solar activity and, to a lesser extent, anthropogenic factors - greenhouse gases and tropospheric sulfate aerosol. As for the period 1946-1996, here natural variations in solar and volcanic activity have only a minor impact on the climate compared to anthropogenic influence.

Influence of the main climate-forming factors on the change in the average global surface temperature. Estimates of contributions indicating ranges of values ​​for: greenhouse gases and sulfate aerosols (white boxes); solar activity (filled with dots) and their combined influence (shaded). The black rectangles show the results of instrumental observations. (Tett S.F.B., Stott P.A. et al. 1999.)

An analysis of the warm biosphere of the Cretaceous period as an analogue of the predicted warming, carried out by N.M. Chumakov, showed that the impact of the main climate-forming factors (in addition to carbon dioxide) is not enough to explain warming of this magnitude in the past. The greenhouse effect of the required magnitude would correspond to a multiple increase in the content of CO 2 in the atmosphere. The impetus for the grandiose climatic changes during this period of the Earth's development, most likely, was a positive feedback between the increase in the temperature of the oceans and seas and the increase in the concentration of atmospheric carbon dioxide.

Much attention in the above review is given to CO 2 as a “fertilizer”. The authors provide data on the acceleration of plant growth with an increased content of carbon dioxide in the atmosphere. In particular, the response of young pine trees, young orange trees, wheat to an increase in environmental CO 2 in the range from 400 to 800 ppm is almost linear and positive. From this, the authors conclude that these data can be easily transferred to different levels of CO 2 enrichment and to different plant species. The authors attribute the increase in the mass of US forests (by 30% since 1950) to the impact of the increasing amount of carbon dioxide in the atmosphere. It is indicated that the growth of CO 2 produces a greater stimulating effect on plants growing in more arid (stressful) conditions. And the intensive growth of plant communities, according to the authors of the review, inevitably leads to an increase in the total mass of animals and has a positive impact on biodiversity in general. This leads to an optimistic conclusion: “As a result of the increase in atmospheric CO 2, we live in more and more favorable conditions environment. Our children will enjoy life on Earth with many more plants and animals. This is a wonderful and unexpected gift from the industrial revolution.”

Nevertheless, it seems to us that many of the data attached to the petition are quite contradictory.

Instead of warming - cooling?

Of course, fluctuations in the level of CO 2 in the atmosphere took place in past epochs, but never have these changes occurred so quickly. But if in the past climatic and biological systems Since the Earth, due to the gradual changes in the composition of the atmosphere, “managed” to move into a new stable state and were in quasi-equilibrium, then in the modern period, with an intense, extremely rapid change in the gas composition of the atmosphere, all terrestrial systems leave the stationary state. And even if we take the position of the authors who deny the hypothesis of global warming, it should be noted that the consequences of such a “leaving the quasi-stationary state”, in particular climate change, can be the most serious.

In addition, according to some forecasts, after reaching the maximum concentration of CO 2 in the atmosphere, it will begin to fall due to a decrease in anthropogenic emissions, absorption of carbon dioxide by the oceans and biota. In this case, the plants will again have to adapt to the changed habitat.

The review certainly correctly noted that modeling the consequences of the growth of CO 2 and other greenhouse gases in the atmosphere, as well as modern theoretical constructions, do not take into account many feedbacks of climate systems, which leads to incorrect forecasts and even, as the authors assure, to the fallacy of the idea itself. global warming. However, in our opinion, this should not lead to the denial possible warming climate, but to the likelihood of unpredictable climatic consequences (for example, the opposite effect - cooling in a number of regions of the globe).

In this regard, some results of mathematical modeling of the complex consequences of a possible change in the Earth's climate are extremely interesting. Experiments with a three-dimensional model of the integrated ocean-atmosphere system, conducted by American researchers, have shown that in response to warming, the thermohaline North Atlantic circulation (North Atlantic Current) is slowing down. The critical concentration of CO 2 that causes this effect lies between two and four pre-industrial values ​​of CO 2 in the atmosphere (it is 280 ppm, while the current concentration is about 360 ppm).

Using a simpler model of the ocean-atmosphere system, specialists conducted a detailed mathematical analysis of the processes described above. According to their calculations, with an increase in carbon dioxide concentration by 1% per year (which corresponds to modern rates), the North Atlantic Current slows down, and at a CO 2 content of 750 ppm, its collapse occurs - a complete cessation of circulation. With a slower increase in the content of carbon dioxide in the atmosphere (and air temperature) - for example, by 0.5% per year, when the concentration reaches 750 ppm, the circulation slows down, but then slowly recovers. In the case of accelerated growth of greenhouse gases in the atmosphere and the associated warming, the North Atlantic Current is destroyed at lower concentrations of CO 2 - 650 ppm. The reasons for the change in the current are that the warming of the surface air causes an increase in the temperature of the surface layers of water, as well as an increase in the pressure of saturated steam in the northern regions, and hence increased condensation, which increases the mass of desalinated water on the surface of the ocean in the North Atlantic. Both processes lead to increased stratification of the water column and slow down (or even make impossible) the constant formation of cold deep waters in the northern part of the Atlantic, when surface waters, cooling and becoming heavier, sink to the bottom regions and then slowly move to the tropics.

Studies of this kind of consequences of atmospheric warming, recently carried out by R. Wood and co-workers, provide an even more interesting picture of possible events. In addition to reducing the total Atlantic transport by 25%, at the current rate of growth of greenhouse gases, there will be a “turn-off” of convection in the Labrador Sea, one of the two northern centers of formation of cold deep waters. Moreover, this can take place already in the period from 2000 to 2030.

Evolution of the maximum dip of the meridional flow of the North Atlantic Current (calculation results for five scenarios of global warming). I - CO 2 concentration reaches 560 ppm, the flow weakens slightly, then recovers; II, IV - the concentration of CO 2 - 650 and 750 ppm, the growth rate of CO 2 1% per year, the circulation is destroyed; III, V - 650 and 750 ppm, growth rate 0.5% per year, the flow weakens, then recovers at a lower level.

These fluctuations in the North Atlantic current can lead to very serious consequences. In particular, if the distribution of heat and temperature flows deviates from the current one in the Atlantic region of the Northern Hemisphere, the average surface air temperatures over Europe may decrease significantly. Moreover, changes in the speed of the North Atlantic Current and the heating of surface waters can reduce the absorption of CO 2 by the ocean (according to the calculations of the mentioned experts - by 30% with a doubling of the concentration of carbon dioxide in the air), which should be taken into account both in forecasts of the future state of the atmosphere and in scenarios for greenhouse gas emissions. Significant changes can also occur in marine ecosystems, including fish and seabird populations, depending not only on specific climatic conditions, but also on nutrients that are brought to the surface by cold ocean currents. Here we want to emphasize the extremely important point mentioned above: the consequences of the growth of greenhouse gases in the atmosphere, as seen, can be much more complex than a uniform warming of the surface atmosphere.

Possible disruption of ecosystems

When modeling the exchange of carbon dioxide, it is also necessary to take into account the impact on gas transfer of the state of the interface between the ocean and the atmosphere. For a number of years, in laboratory and natural experiments, we have studied the intensity of CO 2 transfer in the water-air system. The effect on gas exchange of wind-wave conditions and a dispersed medium formed near the interface between two phases (spray over the surface, foam, air bubbles in the water column) was considered. It turned out that the rate of gas transfer when the nature of the waves changes from gravitational-capillary to gravitational increases significantly. This effect (in addition to the increase in the temperature of the surface layer of the ocean) can make an additional contribution to the flow of carbon dioxide between the ocean and the atmosphere. On the other hand, a significant sink of CO 2 from the atmosphere is precipitation, which, as our studies have shown, intensively leaches carbon dioxide in addition to other gaseous impurities. Calculations using data on the content of dissolved carbon dioxide in rainwater and the annual amount of precipitation showed that 0.2–1 Gt CO 2 can enter the ocean annually with rains, and the total amount of carbon dioxide washed out of the atmosphere can reach 0.7–2.0 Gt .

Returning to the theses of the authors of the appendix to the petition, we note that the most controversial are the data on the beneficial effect of CO 2 growth for green plants. The fact is that there is a number of scientific data, according to which an increase in the concentration of CO 2 in the atmosphere, even without taking into account global warming, can lead to a significant change in the structure and functioning of ecosystems, which can be unfavorable for plants. A positive reaction to increased carbon dioxide in the air, observed in an individual plant, does not necessarily mean that there will be an increased growth of plant communities as a whole.

The authors' thoughts about the role of CO 2 as a growth stimulator are rooted in the details of photosynthesis. Indeed, increasing the concentration of carbon dioxide can intensify this process and, therefore, promote plant growth. So-called C 3 plants benefit from this, which include almost all trees and many of the main crops: rice, wheat, potatoes, legumes. In C 3 -plants, at the first stage of fixation, the CO 2 molecule binds to ribulose diphosphate, which contains a 5-carbon sugar. As a result of the reaction, which occurs under the action of the enzyme ribulose diphosphate carboxylase, a short-lived unstable compound is formed, including a 6-carbon sugar. It breaks down into two derivatives that contain three carbon atoms - hence the name "C 3 -plants". Atmospheric oxygen competes with carbon dioxide for the active center of ribulose diphosphate carboxylase. If O 2 wins, the plant loses energy, since CO 2 fixation does not occur during oxygen utilization. As the concentration of carbon dioxide increases, the probability of its “winning” in competition with O2 for binding to the active center of the enzyme increases. Indeed, in some experiments, when the CO 2 concentration was set at 600 ppm, photorespiration was reduced by 50%, and limiting it means that the plant can use more of its energy to build tissues. However, in these plants, under conditions of increased CO2 concentration, increased photosynthesis is observed at the initial stage of experiments, but after temporary activation, its inhibition occurs. The transport system of a plant is polygenic, depends on many factors (energy, hormonal, etc.) and cannot be quickly reorganized. Therefore, with prolonged exposure of the plant to CO 2 under conditions of high concentration, photosynthesis decreases due to excessive accumulation of starch in chloroplasts.

Nevertheless, in practice, a significant increase in the growth and accumulation of biomass in plants grown at an increased concentration of carbon dioxide has been proven, although over time the intensity of photosynthesis decreases, approaching what is observed in plants living in an atmosphere with a normal gas composition. This discrepancy is explained by the regulatory action of carbon dioxide on the growth function of the plant. Prolonged keeping of a plant at a high concentration of CO 2 is accompanied by an increase in leaf area, stimulation of the growth of second-order shoots, a relative increase in the proportion of roots and storage organs in the plant, and increased tuberization. The growth function is enhanced by the formation of a new photosynthetic apparatus. This indicates a “double” role of CO2 as a substrate in the process of photosynthesis and as a regulator of growth processes. With an increase in the level of carbon dioxide in the atmosphere, a new steady state of the system is established, corresponding to a new level of carbon dioxide, which leads to an increase in yield mainly due to an increase in the volume of the entire photosynthetic system and, to a lesser extent, due to the intensity of photosynthesis per unit leaf area.

A well-known technique for increasing the intensity and productivity of photosynthesis is to increase the concentration of carbon dioxide in greenhouses. This method allows to increase the biomass growth. However, a change in the concentration of CO 2 affects the composition of the end products of photosynthesis: it was found that at high concentrations of 14 CO 2 14 C was included mainly in sugars, and at low concentrations - in amino acids (serine, glycine, etc.).

Since atmospheric carbon dioxide is partially absorbed by precipitation and surface fresh water, the content of CO 2 in the soil solution increases and, as a result, acidification of the environment occurs. In the experiments carried out in our laboratory, an attempt was made to investigate the effects of CO 2 dissolved in water on the accumulation of biomass by plants. Wheat seedlings were grown on standard aqueous nutrient media, in which, in addition to atmospheric carbon, dissolved molecular CO2 and bicarbonate ion in various concentrations served as additional sources of carbon. This was achieved by varying the saturation time of the aqueous solution with gaseous carbon dioxide. It turned out that the initial increase in the concentration of CO 2 in the nutrient medium leads to the stimulation of the ground and root mass of wheat plants. However, with a 2-3-fold excess of the content of dissolved carbon dioxide above the normal one, inhibition of the growth of plant roots was observed with a change in their morphology. Perhaps, with a significant acidification of the environment, there is a decrease in the assimilation of other nutrients (nitrogen, phosphorus, potassium, magnesium, calcium). Thus, the indirect effects of elevated CO 2 concentrations must be taken into account when assessing their effect on plant growth.

The data on the intensification of growth of plants of various species and ages given in the appendix to the petition leave unanswered the question of the conditions for providing the objects of study with biogenic elements. It should be emphasized that the change in CO 2 concentration must be strictly balanced with the consumption of nitrogen, phosphorus, other nutrients, light, water in the production process without disturbing the ecological balance. Thus, enhanced plant growth at high concentrations of CO 2 was observed in a medium rich in nutrients. For example, on wetlands in the estuary of the Chesapeake Bay (southwestern United States), where mainly C 3 plants grow, an increase in CO 2 in the air to 700 ppm led to an intensification of plant growth and an increase in their density. An analysis of more than 700 agronomic studies showed that at high concentrations of CO 2 in the environment, the grain yield was on average 34% higher (where a sufficient amount of fertilizer and water was applied to the soil - resources that are abundant only in developed countries). In order to increase the productivity of agricultural crops in the conditions of rising carbon dioxide in the air, it will obviously be necessary not only to have a significant amount of fertilizers, but also plant protection products (herbicides, insecticides, fungicides, etc.), as well as extensive irrigation works. It is reasonable to fear that the cost of these activities and the consequences for the environment will be too significant and disproportionate.

Studies have also revealed the role of competition in ecosystems, which leads to a decrease in the stimulating effect of high concentrations of CO 2 . Indeed, seedlings of trees of the same species in a temperate climate (New England, USA) and the tropics grew better at a high concentration of atmospheric CO 2 , however, when seedlings of different species were grown together, the productivity of such communities did not increase under the same conditions. It is likely that competition for nutrients inhibits the response of plants to rising carbon dioxide.

A high content of CO 2 in the air can be unfavorable for the so-called C 4 plants, the first products of photosynthesis of which are compounds of four carbon atoms: malic and aspartic acids, oxaloacetate. This class includes many herbs of dry, hot tropical and subtropical regions, agricultural crops - corn, sorghum, sugarcane, etc. C 4 plants have an additional carboxylation mechanism - a kind of pump that concentrates CO 2 near the active center of the enzyme, allowing these plants grow well at normal concentrations of carbon dioxide. In C 4 plants under normal conditions, the energy consumption for photorespiration is much lower and the efficiency of photosynthesis is therefore higher than in C 3 plants. Approximately the same thing happens during photosynthesis, which is characteristic of typical succulents. It is called CAM photosynthesis (Crassulacean Acid Metabolism). CAM plants, like C 4 plants, use both C 3 and C 4 photosynthesis pathways, but differ from C 4 plants in that they are characterized by the separation of these pathways only in time, but not in space, as in C 4 - plants.

Thus, with an increase in the concentration of carbon dioxide, C 3 plants are in a more favorable position than C 4 and CAM plants, and this, in turn, can have very serious consequences. Many C 4 plants will become rare or threatened with extinction. In agroecosystems, when growing C 4 plants, such as corn or sugar cane, an increased concentration of CO 2 can lead to a drop in their productivity, while weeds, which are mainly represented by C 3 plants, will gain an advantage. As a result, a significant reduction in yield is possible.

In the case of warming, increased plant growth, which absorbs atmospheric carbon dioxide, cannot compensate for the accelerated decomposition of organic matter. This is especially important, as it is in high latitude habitats, such as the tundra, that the greatest increase in temperature is expected. In the zone permafrost as the ice melts, more and more peat will be exposed to organic matter-decomposing microorganisms. This process, in turn, will lead to a greater release of CO 2 and CH 4 into the atmosphere. According to estimates, with an increase in summer temperature in the tundra by 4°C, up to 50% of carbon from peat will be additionally released into the atmosphere, despite more intensive plant growth. In this belt, the tundra vegetation itself is an important climate-forming factor; therefore, with warming, the shift of the forest boundary to the north will have serious consequences. The structure of the forage base will change: lichens and mosses, which gravitate to low temperatures, will be replaced by shrubs unsuitable for deer. In addition, an increase in the height of the snow cover will adversely affect the survival of young animals that appear at this time.

The competitive mutual influence of plants with limited nutrient reserves will affect not only natural ecosystems but also on human-created ecosystems. Therefore, the thesis that the future increase in the level of CO 2 in the atmosphere will lead to richer crops and, as a consequence, to an increase in animal productivity, is doubtful.

The study of the adaptive strategy and response of plants to fluctuations in the main factors affecting climate change and environmental characteristics made it possible to refine some forecasts. Back in 1987, a scenario was prepared for the agro-climatic consequences of modern climate change and the growth of CO 2 in the Earth's atmosphere for North America. According to the estimates, with an increase in the concentration of CO 2 to 400 ppm and an increase in the average global temperature near the earth's surface by 0.5°C, the yield of wheat under these conditions will increase by 7–10%. But the increase in air temperatures in the northern latitudes will be especially evident in winter and will cause extremely unfavorable frequent winter thaws, which can lead to a weakening of the frost resistance of winter crops, freezing of crops and damage to their ice crust. The predicted increase in the warm period will necessitate the selection of new varieties with a longer growing season.

As for the forecasts of yields of the main agricultural crops for Russia, the ongoing increase in average surface air temperatures and the increase in CO 2 in the atmosphere, it would seem, should have a positive effect. The impact of only the growth of carbon dioxide in the atmosphere can provide an increase in the productivity of leading agricultural crops - C 3 -plants (cereals, potatoes, beets, etc.) - by an average of 20-30%, while for C 4 -plants (corn, millet , sorghum, amaranth) this growth is insignificant. However, warming will obviously entail a decrease in the level of atmospheric moisture by about 10%, which will complicate agriculture, especially in the southern part of the European territory, in the Volga region, in the steppe regions of Western and Eastern Siberia. Here one can expect not only a decrease in the collection of products per unit area, but also the development of erosion processes (especially wind), deterioration of soil quality, including the loss of humus, salinization, and desertification of large areas. It was found that the saturation of the surface layer of the atmosphere up to 1 m thick with an excess of CO 2 can respond to the “desert effect”. This layer absorbs ascending heat flows, therefore, as a result of its enrichment with carbon dioxide (1.5 times in comparison with the current norm), the local air temperature directly at the earth's surface will become several degrees higher than the average temperature. The intensity of evaporation of moisture from the soil will increase, which will lead to its drying out. Because of this, the production of grain, fodder, sugar beets, potatoes, sunflower seeds, vegetables, etc., may decrease in the country as a whole. As a result, the proportions between the distribution of the population and the production of the main types of agricultural products will change.

Terrestrial ecosystems are thus very sensitive to an increase in CO 2 in the atmosphere, and, by absorbing excess carbon during photosynthesis, they in turn contribute to the growth of atmospheric carbon dioxide. No less important role in the formation of CO2 level in the atmosphere is played by the processes of soil respiration. It is known that modern climate warming causes an increased release of inorganic carbon from soils (especially in northern latitudes). Model calculations carried out to assess the response of terrestrial ecosystems to global climate changes and the level of CO 2 in the atmosphere showed that in the case of only an increase in CO 2 (without climate change), the stimulation of photosynthesis decreases at high CO 2 values, but the release of carbon from soils increases as it accumulates in vegetation and soils. If the atmospheric CO 2 content stabilizes, the net production of ecosystems (the net carbon flux between the biota and the atmosphere) quickly drops to zero, as photosynthesis is compensated by the respiration of plants and soils. According to these calculations, the response of terrestrial ecosystems to climate change without the impact of CO 2 growth could be a decrease in the global carbon flux from the atmosphere to biota due to increased soil respiration in northern ecosystems and a decrease in net primary production in the tropics as a result of a decrease in soil moisture content. This result is supported by estimates that the effect of warming on soil respiration outweighs its effect on plant growth and reduces soil carbon stock. The combined effects of global warming and rising atmospheric CO2 can increase global net ecosystem production and carbon sinks to biota, but significant increases in soil respiration can offset this sink in winter and spring. It is important that these forecasts of the response of terrestrial ecosystems significantly depend on the species composition of plant communities, the availability of nutrients, the age of tree species, and vary significantly within climatic zones.

* * * The data presented in the annex to the petition were intended, as indicated, to prevent the adoption of the document developed at the international meeting in Kyoto 1997 and open for signature from March 1998 to March 1999. As the results of the meeting in Buenos showed - Aires (November 1998), the probability of signing this document by a number of industrialized states, and primarily the United States, is practically absent. In this regard, there is a need to improve the strategy in addressing the problem of global climate change.

The Vice-Director of The World Watch Institute, K. Flavin, considers the creation of an initiative group to be a necessary element of further movement. It will include countries (in particular, Europe and Latin America) that signed the Kyoto Protocol, Largest cities, “constructively thinking corporations and firms” (“British Petroleum”, “Enron Corporation”, “Royal Deutsch Shell”, etc.), actively supporting the limitation of greenhouse gas emissions and involved in the process of limiting their emissions on the basis of emissions trading.

In our opinion, an important contribution to solving this problem could be the introduction of energy-saving technologies and the use of renewable energy sources.

Literature

1 Robinson A.B., Baliunas S.L., Soon W., Robinson Z.W. Environmental Effects of Increased Atmospheric Carbon Dioxide. The petition, along with the review, was sent to research institutes and individual scientists with a request to sign it and further distribute it to colleagues. A copy of the petition and review in Russian and English language available in the edition of Priroda.

2 For more details, see: Sidorenkov N.S. Interannual fluctuations in the atmosphere-ocean-Earth system //Nature. 1998. No. 7. S.26-34.

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16 Mokronosov A.T. Photosynthesis and change in the content of CO 2 in the atmosphere // Priroda. 1994. No. 7. S.25-27.

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In September 2016, the concentration of carbon dioxide in the Earth's atmosphere passed the psychologically significant mark of 400 ppm (parts per million). This makes the plans of developed countries to prevent an increase in temperature on Earth by more than 2 degrees doubtful.

Global warming is an increase in the average temperature of the Earth's climate system. During the period from 1906 to 2005, the average air temperature near the planet's surface increased by 0.74 degrees, and the rate of temperature increase in the second half of the century is about twice as high as for the period as a whole. For the entire period of observations, 2015 is considered the hottest year, when all temperature indicators exceeded those of 2014, the previous record holder, by 0.13 degrees. IN various parts around the globe, temperatures change in different ways. Since 1979, temperatures over land have risen twice as much as over the ocean. This is explained by the fact that the air temperature over the ocean grows more slowly due to its large heat capacity.

The movement of carbon dioxide in the atmosphere

Human activities are considered to be the main cause of global warming. Indirect research methods have shown that until 1850, for one or two thousand years, the temperature remained relatively stable, albeit with some regional fluctuations.

Thus, the beginning of climate change almost coincides with the beginning of the industrial revolution in most Western countries. Greenhouse gas emissions are considered to be the main reason today. The fact is that part of the energy that the planet Earth receives from the Sun is re-radiated back into outer space in the form of thermal radiation.

Greenhouse gases hinder this process by absorbing some of the heat and keeping it in the atmosphere.

The addition of greenhouse gases to the atmosphere leads to even greater heating of the atmosphere and an increase in temperature near the surface of the planet. The main greenhouse gases in the Earth's atmosphere are carbon dioxide (CO 2) and methane (CH 4). As a result of the industrial activity of mankind, the concentration of these gases in the air is growing, which leads to an annual increase in temperature.

Since climate warming threatens literally all of humanity, attempts are made repeatedly in the world to bring this process under control. Until 2012, the Kyoto Protocol was the main global agreement to combat global warming.

It covered more than 160 countries of the world and covered 55% of the world's greenhouse gas emissions. However, after the end of the first stage of the Kyoto Protocol, the participating countries could not agree on further actions. In part, the drafting of the second stage of the treaty was hampered by the fact that many participants avoid using the budget approach to determine their obligations in relation to CO 2 emissions. CO 2 emission budget - the amount of emissions over a certain period of time, which is calculated from the temperature that participants must not exceed.

According to the decisions taken in Durban, no binding climate agreement will be in place until 2020, despite urgent efforts to reduce gas emissions and reduce emissions. Studies show that at present the only way to provide a "reasonable probability" of limiting warming to 2 degrees (characterizing dangerous climate change) will be to limit the economies of developed countries and their transition to an anti-growth strategy.

And in September 2016, according to the Mauna Loa Observatory, another psychological barrier of CO 2 greenhouse gas emissions was overcome - 400 ppm (parts per million). It must be said that this value was repeatedly exceeded before,

but September is traditionally considered the month with the lowest concentration of CO 2 in the Northern Hemisphere.

This is explained by the fact that green vegetation has time to absorb a certain amount of greenhouse gas from the atmosphere during the summer before the leaves fall from the trees and some of the CO 2 returns. Therefore, if the psychologically important threshold of 400 ppm was exceeded in September, then, most likely, monthly indicators will never be lower than this value.

“Is it possible that in October this year the concentration will decrease compared to September? Completely ruled out

Ralph Keeling of the Scripps Institution of Oceanography in San Diego explains on his blog. “Short-term drops in the concentration level are possible, but the monthly average values ​​will now always exceed 400 ppm.”

Keeling also notes that tropical cyclones can reduce the level of CO 2 concentration by a short time. Gavin Schmidt, chief climate scientist, agrees: “At best, you can expect some kind of balance, and CO 2 levels will not rise too quickly. But, in my opinion, CO 2 will never fall below 400 ppm again.”

According to the forecast, by 2099 the concentration of CO 2 on Earth will be 900 ppm, which will be about 0.1% of the entire atmosphere of our planet. As a result, average daily temperatures in cities like Jerusalem, New York, Los Angeles and Mumbai will be close to +45°C. In London, Paris and Moscow, temperatures will exceed +30°C in summer.

Soda, volcano, Venus, refrigerator - what do they have in common? Carbon dioxide. We have collected for you the most interesting information about one of the most important chemical compounds on the ground.

What is carbon dioxide

Carbon dioxide is known mainly for its gaseous state, i.e. as carbon dioxide with simple chemical formula CO2. In this form, it exists under normal conditions - at atmospheric pressure and "normal" temperatures. But at increased pressure, over 5,850 kPa (such, for example, the pressure at a sea depth of about 600 m), this gas turns into a liquid. And with strong cooling (minus 78.5 ° C), it crystallizes and becomes the so-called dry ice, which is widely used in trade for storing frozen foods in refrigerators.

Liquid carbon dioxide and dry ice are produced and used in human activities, but these forms are unstable and break down easily.

But gaseous carbon dioxide is ubiquitous: it is released during the respiration of animals and plants and is an important part of chemical composition atmosphere and ocean.

Properties of carbon dioxide

Carbon dioxide CO2 is colorless and odorless. Under normal conditions, it has no taste. However, when inhaling high concentrations of carbon dioxide, a sour taste can be felt in the mouth, caused by the fact that carbon dioxide dissolves on mucous membranes and in saliva, forming a weak solution of carbonic acid.

By the way, it is the ability of carbon dioxide to dissolve in water that is used to make sparkling waters. Bubbles of lemonade - the same carbon dioxide. The first apparatus for saturating water with CO2 was invented as early as 1770, and already in 1783, the enterprising Swiss Jacob Schwepp began the industrial production of soda (the Schweppes trademark still exists).

Carbon dioxide is 1.5 times heavier than air, so it tends to “settle” in its lower layers if the room is poorly ventilated. The “dog cave” effect is known, where CO2 is released directly from the ground and accumulates at a height of about half a meter. An adult, getting into such a cave, at the height of his height does not feel an excess of carbon dioxide, but dogs find themselves right in a thick layer of carbon dioxide and are poisoned.

CO2 does not support combustion, so it is used in fire extinguishers and fire suppression systems. The trick with extinguishing a burning candle with the contents of an allegedly empty glass (but in fact with carbon dioxide) is based precisely on this property of carbon dioxide.

Carbon dioxide in nature: natural sources

Carbon dioxide is produced in nature from various sources:

• Breathing of animals and plants.
  Every schoolchild knows that plants absorb carbon dioxide CO2 from the air and use it in photosynthesis. Some housewives are trying to atone for shortcomings with an abundance of indoor plants. However, plants not only absorb but also release carbon dioxide in the absence of light as part of the respiration process. Therefore, a jungle in a poorly ventilated bedroom is not a good idea: at night, CO2 levels will rise even more.
• Volcanic activity.
  Carbon dioxide is part of volcanic gases. In areas with high volcanic activity CO2 can be emitted directly from the ground - from cracks and fissures called mofets. The concentration of carbon dioxide in mofet valleys is so high that many small animals die when they get there.
• decomposition of organic matter.
  Carbon dioxide is formed during combustion and decay of organic matter. Volumetric natural emissions of carbon dioxide accompany forest fires.

Carbon dioxide is "stored" in nature in the form of carbon compounds in minerals: coal, oil, peat, limestone. Huge reserves of CO2 are found in dissolved form in the world's oceans.

The release of carbon dioxide from an open reservoir can lead to a limnological catastrophe, as happened, for example, in 1984 and 1986. in lakes Manun and Nyos in Cameroon. Both lakes were formed on the site of volcanic craters - now they are extinct, but in the depths, volcanic magma still emits carbon dioxide, which rises to the waters of the lakes and dissolves in them. As a result of a number of climatic and geological processes, the concentration of carbon dioxide in the waters exceeded the critical value. Was released into the atmosphere great amount carbon dioxide, which, like an avalanche, descended down the mountain slopes. About 1,800 people became victims of limnological disasters on the Cameroonian lakes.

Artificial sources of carbon dioxide

The main anthropogenic sources of carbon dioxide are:

• industrial emissions associated with combustion processes;
• automobile transport.

Despite the fact that the share of environmentally friendly transport in the world is growing, the vast majority of the world's population will not soon be able (or willing) to switch to new cars.

Active deforestation for industrial purposes also leads to an increase in the concentration of carbon dioxide CO2 in the air.

CO2 is one of the end products of metabolism (the breakdown of glucose and fats). It is secreted in the tissues and carried by hemoglobin to the lungs, through which it is exhaled. In the air exhaled by a person, there is about 4.5% carbon dioxide (45,000 ppm) - 60-110 times more than in the inhaled air.

Carbon dioxide plays an important role in the regulation of blood supply and respiration. An increase in the level of CO2 in the blood causes the capillaries to expand, allowing more blood to pass through, which delivers oxygen to the tissues and removes carbon dioxide.

The respiratory system is also stimulated by an increase in carbon dioxide, and not by a lack of oxygen, as it might seem. In fact, the lack of oxygen is not felt by the body for a long time, and it is quite possible that in rarefied air a person will lose consciousness before he feels a lack of air. The stimulating property of CO2 is used in artificial respiration devices: there, carbon dioxide is mixed with oxygen to "start" the respiratory system.

Carbon dioxide and us: why is CO2 dangerous?

Carbon dioxide is as essential to the human body as oxygen. But just like with oxygen, an excess of carbon dioxide harms our well-being.

A high concentration of CO2 in the air leads to intoxication of the body and causes a state of hypercapnia. In hypercapnia, a person experiences difficulty breathing, nausea, headache, and may even pass out. If the carbon dioxide content does not decrease, then the turn comes - oxygen starvation. The fact is that both carbon dioxide and oxygen move around the body on the same "transport" - hemoglobin. Normally, they "travel" together, attaching to different places on the hemoglobin molecule. However, an increased concentration of carbon dioxide in the blood reduces the ability of oxygen to bind to hemoglobin. The amount of oxygen in the blood decreases and hypoxia occurs.

Such unhealthy consequences for the body occur when inhaling air with a CO2 content of more than 5,000 ppm (this can be the air in mines, for example). To be fair, in ordinary life we practically do not encounter such air. However, even a much lower concentration of carbon dioxide is not good for health.

According to the findings of some, already 1,000 ppm CO2 causes fatigue and headache in half of the subjects. Many people begin to feel closeness and discomfort even earlier. With a further increase in the concentration of carbon dioxide to 1,500 - 2,500 ppm, the brain is "lazy" to take the initiative, process information and make decisions.

And if the level of 5,000 ppm is almost impossible in everyday life, then 1,000 and even 2,500 ppm can easily be part of reality. modern man. Ours showed that in sparsely ventilated classrooms, CO2 levels stay above 1,500 ppm most of the time, and sometimes jump above 2,000 ppm. There is every reason to believe that the situation is similar in many offices and even apartments.

Physiologists consider 800 ppm as a safe level of carbon dioxide for human well-being.

Another study found a link between CO2 levels and oxidative stress: the higher the level of carbon dioxide, the more we suffer from, which destroys the cells of our body.

Carbon dioxide in the earth's atmosphere

In the atmosphere of our planet, there is only about 0.04% CO2 (this is approximately 400 ppm), and more recently it was even less: carbon dioxide crossed the mark of 400 ppm only in the fall of 2016. Scientists attribute the rise in the level of CO2 in the atmosphere to industrialization: in the middle of the 18th century, on the eve of the industrial revolution, it was only about 270 ppm.